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<div class="section">
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
<a name="boost_asio.history"></a><a class="link" href="history.html" title="Revision History">Revision History</a>
</h2></div></div></div>
<h4>
<a name="boost_asio.history.h0"></a>
      <span><a name="boost_asio.history.asio_1_8_3___boost_1_53"></a></span><a class="link" href="history.html#boost_asio.history.asio_1_8_3___boost_1_53">Asio
      1.8.3 / Boost 1.53</a>
    </h4>
<div class="itemizedlist"><ul class="itemizedlist" type="disc">
<li class="listitem">
          Fixed some 64-to-32-bit conversion warnings (<a href="https://svn.boost.org/trac/boost/ticket/7459" target="_top">#7459</a>).
        </li>
<li class="listitem">
          Fixed some small errors in documentation and comments (<a href="https://svn.boost.org/trac/boost/ticket/7761" target="_top">#7761</a>).
        </li>
<li class="listitem">
          Fixed an error in the example embedded in <code class="computeroutput"><span class="identifier">basic_socket</span><span class="special">::</span><span class="identifier">get_option</span></code>'s
          documentation (<a href="https://svn.boost.org/trac/boost/ticket/7562" target="_top">#7562</a>).
        </li>
<li class="listitem">
          Changed to use <code class="computeroutput"><span class="keyword">long</span></code> rather
          than <code class="computeroutput"><span class="keyword">int</span></code> for SSL_CTX options,
          to match OpenSSL (<a href="https://svn.boost.org/trac/boost/ticket/7209" target="_top">#7209</a>).
        </li>
<li class="listitem">
          Changed to use <code class="computeroutput"><span class="identifier">_snwprintf</span></code>
          to address a compile error due to the changed <code class="computeroutput"><span class="identifier">swprintf</span></code>
          signature in recent versions of MinGW (<a href="https://svn.boost.org/trac/boost/ticket/7373" target="_top">#7373</a>).
        </li>
<li class="listitem">
          Fixed a deadlock that can occur on Windows when shutting down a pool of
          <code class="computeroutput"><span class="identifier">io_service</span></code> threads due
          to running out of work (<a href="https://svn.boost.org/trac/boost/ticket/7552" target="_top">#7552</a>).
        </li>
<li class="listitem">
          Enabled the <code class="computeroutput"><span class="identifier">noexcept</span></code> qualifier
          for error categories (<a href="https://svn.boost.org/trac/boost/ticket/7797" target="_top">#7797</a>).
        </li>
<li class="listitem">
          Changed UNIX domain socket example to treat errors from <code class="computeroutput"><span class="identifier">accept</span></code>
          as non-fatal (<a href="https://svn.boost.org/trac/boost/ticket/7488" target="_top">#7488</a>).
        </li>
<li class="listitem">
          Added a small block recycling optimisation to improve default memory allocation
          behaviour.
        </li>
</ul></div>
<h4>
<a name="boost_asio.history.h1"></a>
      <span><a name="boost_asio.history.asio_1_8_2___boost_1_51"></a></span><a class="link" href="history.html#boost_asio.history.asio_1_8_2___boost_1_51">Asio
      1.8.2 / Boost 1.51</a>
    </h4>
<div class="itemizedlist"><ul class="itemizedlist" type="disc">
<li class="listitem">
          Fixed an incompatibility between <code class="computeroutput"><span class="identifier">ip</span><span class="special">::</span><span class="identifier">tcp</span><span class="special">::</span><span class="identifier">iostream</span></code>
          and C++11 (<a href="https://svn.boost.org/trac/boost/ticket/7162" target="_top">#7162</a>).
        </li>
<li class="listitem">
          Decorated GCC attribute names with underscores to prevent interaction with
          user-defined macros (<a href="https://svn.boost.org/trac/boost/ticket/6415" target="_top">#6415</a>).
        </li>
<li class="listitem">
          Added missing <code class="computeroutput"><span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">cctype</span><span class="special">&gt;</span></code>, needed for some versions of MinGW.
        </li>
<li class="listitem">
          Changed to use <code class="literal">gcc</code>'s atomic builtins on ARM CPUs, when
          available (<a href="https://svn.boost.org/trac/boost/ticket/7140" target="_top">#7140</a>).
        </li>
<li class="listitem">
          Changed strand destruction to be a no-op, to allow strand objects to be
          destroyed after their associated <code class="computeroutput"><span class="identifier">io_service</span></code>
          has been destroyed.
        </li>
<li class="listitem">
          Added support for some newer versions of glibc which provide the <code class="computeroutput"><span class="identifier">epoll_create1</span><span class="special">()</span></code>
          function but always fail with <code class="computeroutput"><span class="identifier">ENOSYS</span></code>
          (<a href="https://svn.boost.org/trac/boost/ticket/7012" target="_top">#7012</a>).
        </li>
<li class="listitem">
          Changed the SSL implementation to throw an exception if SSL engine initialisation
          fails (<a href="https://svn.boost.org/trac/boost/ticket/6303" target="_top">#6303</a>).
        </li>
<li class="listitem">
          Fixed another regression in <code class="computeroutput"><span class="identifier">buffered_write_stream</span></code>
          (<a href="https://svn.boost.org/trac/boost/ticket/6310" target="_top">#6310</a>).
        </li>
<li class="listitem">
          Implemented various minor performance improvements, primarily targeted
          at Linux x86 and x86-64 platforms.
        </li>
</ul></div>
<h4>
<a name="boost_asio.history.h2"></a>
      <span><a name="boost_asio.history.asio_1_8_1___boost_1_50"></a></span><a class="link" href="history.html#boost_asio.history.asio_1_8_1___boost_1_50">Asio
      1.8.1 / Boost 1.50</a>
    </h4>
<div class="itemizedlist"><ul class="itemizedlist" type="disc">
<li class="listitem">
          Changed the <code class="computeroutput"><span class="identifier">epoll_reactor</span></code>
          backend to do lazy registration for <code class="computeroutput"><span class="identifier">EPOLLOUT</span></code>
          events.
        </li>
<li class="listitem">
          Fixed the <code class="computeroutput"><span class="identifier">epoll_reactor</span></code>
          handling of out-of-band data, which was broken by an incomplete fix in
          the last release.
        </li>
<li class="listitem">
          Changed Asio's SSL wrapper to respect OpenSSL's <code class="computeroutput"><span class="identifier">OPENSSL_NO_ENGINE</span></code>
          feature test <code class="computeroutput"><span class="preprocessor">#define</span></code>
          (<a href="https://svn.boost.org/trac/boost/ticket/6432" target="_top">#6432</a>).
        </li>
<li class="listitem">
          Fixed <code class="computeroutput"><span class="identifier">windows</span><span class="special">::</span><span class="identifier">object_handle</span></code> so that it works with Windows
          compilers that support C++11 move semantics (such as <code class="literal">g++</code>).
        </li>
<li class="listitem">
          Improved the performance of strand rescheduling.
        </li>
<li class="listitem">
          Added support for <code class="literal">g++</code> 4.7 when compiling in C++11 mode
          (<a href="https://svn.boost.org/trac/boost/ticket/6620" target="_top">#6620</a>).
        </li>
<li class="listitem">
          Fixed a problem where <code class="computeroutput"><span class="identifier">signal_set</span></code>
          handlers were not being delivered when the <code class="computeroutput"><span class="identifier">io_service</span></code>
          was constructed with a <code class="computeroutput"><span class="identifier">concurrency_hint</span></code>
          of 1 (<a href="https://svn.boost.org/trac/boost/ticket/6657" target="_top">#6657</a>).
        </li>
</ul></div>
<h4>
<a name="boost_asio.history.h3"></a>
      <span><a name="boost_asio.history.asio_1_8_0___boost_1_49"></a></span><a class="link" href="history.html#boost_asio.history.asio_1_8_0___boost_1_49">Asio
      1.8.0 / Boost 1.49</a>
    </h4>
<div class="itemizedlist"><ul class="itemizedlist" type="disc">
<li class="listitem">
          Added a new class template <code class="computeroutput"><span class="identifier">basic_waitable_timer</span></code>
          based around the C++11 clock type requirements. It may be used with the
          clocks from the C++11 <code class="computeroutput"><span class="special">&lt;</span><span class="identifier">chrono</span><span class="special">&gt;</span></code>
          library facility or, if those are not available, Boost.Chrono. The typedefs
          <code class="computeroutput"><span class="identifier">high_resolution_timer</span></code>,
          <code class="computeroutput"><span class="identifier">steady_timer</span></code> and <code class="computeroutput"><span class="identifier">system_timer</span></code> may be used to create timer
          objects for the standard clock types.
        </li>
<li class="listitem">
          Added a new <code class="computeroutput"><span class="identifier">windows</span><span class="special">::</span><span class="identifier">object_handle</span></code> class for performing waits
          on Windows kernel objects. Thanks go to Boris Schaeling for contributing
          substantially to the development of this feature.
        </li>
<li class="listitem">
          On Linux, <code class="computeroutput"><span class="identifier">connect</span><span class="special">()</span></code>
          can return EAGAIN in certain circumstances. Remapped this to another error
          so that it doesn't look like a non-blocking operation (<a href="https://svn.boost.org/trac/boost/ticket/6048" target="_top">#6048</a>).
        </li>
<li class="listitem">
          Fixed a compile error on NetBSD (<a href="https://svn.boost.org/trac/boost/ticket/6098" target="_top">#6098</a>).
        </li>
<li class="listitem">
          Fixed deadlock on Mac OS X (<a href="https://svn.boost.org/trac/boost/ticket/6275" target="_top">#6275</a>).
        </li>
<li class="listitem">
          Fixed a regression in <code class="computeroutput"><span class="identifier">buffered_write_stream</span></code>
          (<a href="https://svn.boost.org/trac/boost/ticket/6310" target="_top">#6310</a>).
        </li>
<li class="listitem">
          Fixed a non-paged pool "leak" on Windows when an <code class="computeroutput"><span class="identifier">io_service</span></code> is repeatedly run without
          anything to do (<a href="https://svn.boost.org/trac/boost/ticket/6321" target="_top">#6321</a>).
        </li>
<li class="listitem">
          Reverted earlier change to allow some speculative operations to be performed
          without holding the lock, as it introduced a race condition in some multithreaded
          scenarios.
        </li>
<li class="listitem">
          Fixed a bug where the second buffer in an array of two buffers may be ignored
          if the first buffer is empty.
        </li>
</ul></div>
<h4>
<a name="boost_asio.history.h4"></a>
      <span><a name="boost_asio.history.asio_1_6_1___boost_1_48"></a></span><a class="link" href="history.html#boost_asio.history.asio_1_6_1___boost_1_48">Asio
      1.6.1 / Boost 1.48</a>
    </h4>
<div class="itemizedlist"><ul class="itemizedlist" type="disc">
<li class="listitem">
          Implemented various performance improvements, including:
          <div class="itemizedlist"><ul class="itemizedlist" type="circle">
<li class="listitem">
                Using thread-local operation queues in single-threaded use cases
                (i.e. when <code class="computeroutput"><span class="identifier">concurrency_hint</span></code>
                is 1) to eliminate a lock/unlock pair.
              </li>
<li class="listitem">
                Allowing some <code class="computeroutput"><span class="identifier">epoll_reactor</span></code>
                speculative operations to be performed without holding the lock.
              </li>
<li class="listitem">
                Improving locality of reference by performing an <code class="computeroutput"><span class="identifier">epoll_reactor</span></code>'s
                I/O operation immediately before the corresponding handler is called.
                This also improves scalability across CPUs when multiple threads
                are running the <code class="computeroutput"><span class="identifier">io_service</span></code>.
              </li>
<li class="listitem">
                Specialising asynchronous read and write operations for buffer sequences
                that are arrays (<code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">array</span></code>
                or <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">array</span></code>) of exactly two buffers.
              </li>
</ul></div>
        </li>
<li class="listitem">
          Fixed a compile error in the regex overload of <code class="computeroutput"><span class="identifier">async_read_until</span></code>
          (<a href="https://svn.boost.org/trac/boost/ticket/5688" target="_top">#5688</a>).
        </li>
<li class="listitem">
          Fixed a Windows-specific compile error by explicitly specifying the <code class="computeroutput"><span class="identifier">signal</span><span class="special">()</span></code>
          function from the global namespace (<a href="https://svn.boost.org/trac/boost/ticket/5722" target="_top">#5722</a>).
        </li>
<li class="listitem">
          Changed the <code class="computeroutput"><span class="identifier">deadline_timer</span></code>
          implementation so that it does not read the clock unless the timer heap
          is non-empty.
        </li>
<li class="listitem">
          Changed the SSL stream's buffers' sizes so that they are large enough to
          hold a complete TLS record (<a href="https://svn.boost.org/trac/boost/ticket/5854" target="_top">#5854</a>).
        </li>
<li class="listitem">
          Fixed the behaviour of the synchronous <code class="computeroutput"><span class="identifier">null_buffers</span></code>
          operations so that they obey the user's non-blocking setting (<a href="https://svn.boost.org/trac/boost/ticket/5756" target="_top">#5756</a>).
        </li>
<li class="listitem">
          Changed to set the size of the select <code class="computeroutput"><span class="identifier">fd_set</span></code>
          at runtime when using Windows.
        </li>
<li class="listitem">
          Disabled an MSVC warning due to const qualifier being applied to function
          type.
        </li>
<li class="listitem">
          Fixed a crash that occurs when using the Intel C++ compiler (<a href="https://svn.boost.org/trac/boost/ticket/5763" target="_top">#5763</a>).
        </li>
<li class="listitem">
          Changed the initialisation of the OpenSSL library so that it supports all
          available algorithms.
        </li>
<li class="listitem">
          Fixed the SSL error mapping used when the session is gracefully shut down.
        </li>
<li class="listitem">
          Added some latency test programs.
        </li>
<li class="listitem">
          Clarified that a read operation ends when the buffer is full (<a href="https://svn.boost.org/trac/boost/ticket/5999" target="_top">#5999</a>).
        </li>
<li class="listitem">
          Fixed an exception safety issue in <code class="computeroutput"><span class="identifier">epoll_reactor</span></code>
          initialisation (<a href="https://svn.boost.org/trac/boost/ticket/6006" target="_top">#6006</a>).
        </li>
<li class="listitem">
          Made the number of strand implementations configurable by defining <code class="computeroutput"><span class="identifier">BOOST_ASIO_STRAND_IMPLEMENTATIONS</span></code> to
          the desired number.
        </li>
<li class="listitem">
          Added support for a new <code class="computeroutput"><span class="identifier">BOOST_ASIO_ENABLE_SEQUENTIAL_STRAND_ALLOCATION</span></code>
          flag which switches the allocation of strand implementations to use a round-robin
          approach rather than hashing.
        </li>
<li class="listitem">
          Fixed potential strand starvation issue that can occur when <code class="computeroutput"><span class="identifier">strand</span><span class="special">.</span><span class="identifier">post</span><span class="special">()</span></code>
          is used.
        </li>
</ul></div>
<h4>
<a name="boost_asio.history.h5"></a>
      <span><a name="boost_asio.history.asio_1_6_0___boost_1_47"></a></span><a class="link" href="history.html#boost_asio.history.asio_1_6_0___boost_1_47">Asio
      1.6.0 / Boost 1.47</a>
    </h4>
<div class="itemizedlist"><ul class="itemizedlist" type="disc">
<li class="listitem">
          Added support for signal handling, using a new class called <code class="computeroutput"><span class="identifier">signal_set</span></code>. Programs may add one or more
          signals to the set, and then perform an <code class="computeroutput"><span class="identifier">async_wait</span><span class="special">()</span></code> operation. The specified handler will
          be called when one of the signals occurs. The same signal number may be
          registered with multiple <code class="computeroutput"><span class="identifier">signal_set</span></code>
          objects, however the signal number must be used only with Asio. Addresses
          <a href="https://svn.boost.org/trac/boost/ticket/2879" target="_top">#2879</a>.
        </li>
<li class="listitem">
          Added handler tracking, a new debugging aid. When enabled by defining
          <code class="computeroutput"><span class="identifier">BOOST_ASIO_ENABLE_HANDLER_TRACKING</span></code>,
          Asio writes debugging output to the standard error stream. The output records
          asynchronous operations and the relationships between their handlers. It
          may be post-processed using the included <code class="literal">handlerviz.pl</code>
          tool to create a visual representation of the handlers (requires GraphViz).
        </li>
<li class="listitem">
          Added support for timeouts on socket iostreams, such as <code class="computeroutput"><span class="identifier">ip</span><span class="special">::</span><span class="identifier">tcp</span><span class="special">::</span><span class="identifier">iostream</span></code>.
          A timeout is set by calling <code class="computeroutput"><span class="identifier">expires_at</span><span class="special">()</span></code> or <code class="computeroutput"><span class="identifier">expires_from_now</span><span class="special">()</span></code> to establish a deadline. Any socket operations
          which occur past the deadline will put the iostream into a bad state.
        </li>
<li class="listitem">
          Added a new <code class="computeroutput"><span class="identifier">error</span><span class="special">()</span></code>
          member function to socket iostreams, for retrieving the error code from
          the most recent system call.
        </li>
<li class="listitem">
          Added a new <code class="computeroutput"><span class="identifier">basic_deadline_timer</span><span class="special">::</span><span class="identifier">cancel_one</span><span class="special">()</span></code> function. This function lets you cancel
          a single waiting handler on a timer. Handlers are cancelled in FIFO order.
        </li>
<li class="listitem">
          Added a new <code class="computeroutput"><span class="identifier">transfer_exactly</span><span class="special">()</span></code> completion condition. This can be used
          to send or receive a specified number of bytes even if the total size of
          the buffer (or buffer sequence) is larger.
        </li>
<li class="listitem">
          Added new free functions <code class="computeroutput"><span class="identifier">connect</span><span class="special">()</span></code> and <code class="computeroutput"><span class="identifier">async_connect</span><span class="special">()</span></code>. These operations try each endpoint in
          a list until the socket is successfully connected, and are useful for creating
          TCP clients that work with both IPv4 and IPv6.
        </li>
<li class="listitem">
          Extended the <code class="computeroutput"><span class="identifier">buffer_size</span><span class="special">()</span></code> function so that it works for buffer
          sequences in addition to individual buffers.
        </li>
<li class="listitem">
          Added a new <code class="computeroutput"><span class="identifier">buffer_copy</span><span class="special">()</span></code> function that can be used to copy the
          raw bytes between individual buffers and buffer sequences.
        </li>
<li class="listitem">
          Added new non-throwing overloads of <code class="computeroutput"><span class="identifier">read</span><span class="special">()</span></code>, <code class="computeroutput"><span class="identifier">read_at</span><span class="special">()</span></code>, <code class="computeroutput"><span class="identifier">write</span><span class="special">()</span></code> and <code class="computeroutput"><span class="identifier">write_at</span><span class="special">()</span></code> that do not require a completion condition.
        </li>
<li class="listitem">
          Added friendlier compiler errors for when a completion handler does not
          meet the necessary type requirements. When C++0x is available (currently
          supported for <code class="literal">g++</code> 4.5 or later, and MSVC 10), <code class="computeroutput"><span class="identifier">static_assert</span></code> is also used to generate
          an informative error message. This checking may be disabled by defining
          <code class="computeroutput"><span class="identifier">BOOST_ASIO_DISABLE_HANDLER_TYPE_REQUIREMENTS</span></code>.
        </li>
<li class="listitem">
          Added a new, completely rewritten SSL implementation. The new implementation
          compiles faster, shows substantially improved performance, and supports
          custom memory allocation and handler invocation. It includes new API features
          such as certificate verification callbacks and has improved error reporting.
          The new implementation is source-compatible with the old for most uses.
          However, if necessary, the old implementation may still be used by defining
          <code class="computeroutput"><span class="identifier">BOOST_ASIO_ENABLE_OLD_SSL</span></code>.
          Addresses <a href="https://svn.boost.org/trac/boost/ticket/3702" target="_top">#3702</a>,
          <a href="https://svn.boost.org/trac/boost/ticket/3958" target="_top">#3958</a>.
        </li>
<li class="listitem">
          Changed the separate compilation support such that, to use Asio's SSL capabilities,
          you should also include <code class="computeroutput"><span class="identifier">boost</span><span class="special">/</span><span class="identifier">asio</span><span class="special">/</span><span class="identifier">ssl</span><span class="special">/</span><span class="identifier">impl</span><span class="special">/</span><span class="identifier">src</span><span class="special">.</span><span class="identifier">hpp</span></code>
          in one source file in your program.
        </li>
<li class="listitem">
          Changed the SSL implementation to support build environments where SSL
          v2 is explicitly disabled (<a href="https://svn.boost.org/trac/boost/ticket/5453" target="_top">#5453</a>).
        </li>
<li class="listitem">
          Made the <code class="computeroutput"><span class="identifier">is_loopback</span><span class="special">()</span></code>,
          <code class="computeroutput"><span class="identifier">is_unspecified</span><span class="special">()</span></code>
          and <code class="computeroutput"><span class="identifier">is_multicast</span><span class="special">()</span></code>
          functions consistently available across the <code class="computeroutput"><span class="identifier">ip</span><span class="special">::</span><span class="identifier">address</span></code>,
          <code class="computeroutput"><span class="identifier">ip</span><span class="special">::</span><span class="identifier">address_v4</span></code> and <code class="computeroutput"><span class="identifier">ip</span><span class="special">::</span><span class="identifier">address_v6</span></code>
          classes (<a href="https://svn.boost.org/trac/boost/ticket/3939" target="_top">#3939</a>).
        </li>
<li class="listitem">
          Added new <code class="computeroutput"><span class="identifier">non_blocking</span><span class="special">()</span></code> functions for managing the non-blocking
          behaviour of a socket or descriptor. The <code class="computeroutput"><span class="identifier">io_control</span><span class="special">()</span></code> commands named <code class="computeroutput"><span class="identifier">non_blocking_io</span></code>
          are now deprecated in favour of these new functions.
        </li>
<li class="listitem">
          Added new <code class="computeroutput"><span class="identifier">native_non_blocking</span><span class="special">()</span></code> functions for managing the non-blocking
          mode of the underlying socket or descriptor. These functions are intended
          to allow the encapsulation of arbitrary non-blocking system calls as asynchronous
          operations, in a way that is transparent to the user of the socket object.
          The functions have no effect on the behaviour of the synchronous operations
          of the socket or descriptor.
        </li>
<li class="listitem">
          Added the <code class="computeroutput"><span class="identifier">io_control</span><span class="special">()</span></code>
          member function for socket acceptors (<a href="https://svn.boost.org/trac/boost/ticket/3297" target="_top">#3297</a>).
        </li>
<li class="listitem">
          Added a <code class="computeroutput"><span class="identifier">release</span><span class="special">()</span></code>
          member function to posix descriptors. This function releases ownership
          of the underlying native descriptor to the caller. Addresses <a href="https://svn.boost.org/trac/boost/ticket/3900" target="_top">#3900</a>.
        </li>
<li class="listitem">
          Added support for sequenced packet sockets (<code class="computeroutput"><span class="identifier">SOCK_SEQPACKET</span></code>).
        </li>
<li class="listitem">
          Added a new <code class="computeroutput"><span class="identifier">io_service</span><span class="special">::</span><span class="identifier">stopped</span><span class="special">()</span></code> function that can be used to determine
          whether the <code class="computeroutput"><span class="identifier">io_service</span></code>
          has stopped (i.e. a <code class="computeroutput"><span class="identifier">reset</span><span class="special">()</span></code> call is needed prior to any further calls
          to <code class="computeroutput"><span class="identifier">run</span><span class="special">()</span></code>,
          <code class="computeroutput"><span class="identifier">run_one</span><span class="special">()</span></code>,
          <code class="computeroutput"><span class="identifier">poll</span><span class="special">()</span></code>
          or <code class="computeroutput"><span class="identifier">poll_one</span><span class="special">()</span></code>).
        </li>
<li class="listitem">
          For consistency with the C++0x standard library, deprecated the <code class="computeroutput"><span class="identifier">native_type</span></code> typedefs in favour of <code class="computeroutput"><span class="identifier">native_handle_type</span></code>, and the <code class="computeroutput"><span class="identifier">native</span><span class="special">()</span></code>
          member functions in favour of <code class="computeroutput"><span class="identifier">native_handle</span><span class="special">()</span></code>.
        </li>
<li class="listitem">
          Added support for C++0x move construction and assignment to sockets, serial
          ports, POSIX descriptors and Windows handles.
        </li>
<li class="listitem">
          Reduced the copying of handler function objects.
        </li>
<li class="listitem">
          Added support for C++0x move construction to further reduce (and in some
          cases eliminate) copying of handler objects.
        </li>
<li class="listitem">
          Added support for the <code class="computeroutput"><span class="identifier">fork</span><span class="special">()</span></code> system call. Programs that use <code class="computeroutput"><span class="identifier">fork</span><span class="special">()</span></code>
          must call <code class="computeroutput"><span class="identifier">io_service</span><span class="special">.</span><span class="identifier">notify_fork</span><span class="special">()</span></code>
          at the appropriate times. Two new examples have been added showing how
          to use this feature. Addresses <a href="https://svn.boost.org/trac/boost/ticket/3238" target="_top">#3238</a>,
          <a href="https://svn.boost.org/trac/boost/ticket/4162" target="_top">#4162</a>.
        </li>
<li class="listitem">
          Cleaned up the handling of errors reported by the <code class="computeroutput"><span class="identifier">close</span><span class="special">()</span></code> system call. In particular, assume that
          most operating systems won't have <code class="computeroutput"><span class="identifier">close</span><span class="special">()</span></code> fail with <code class="computeroutput"><span class="identifier">EWOULDBLOCK</span></code>,
          but if it does then set the blocking mode and restart the call. If any
          other error occurs, assume the descriptor is closed. Addresses <a href="https://svn.boost.org/trac/boost/ticket/3307" target="_top">#3307</a>.
        </li>
<li class="listitem">
          Added new <code class="computeroutput"><span class="identifier">asio</span><span class="special">::</span><span class="identifier">buffer</span><span class="special">()</span></code>
          overloads for <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">array</span></code>, when available.
        </li>
<li class="listitem">
          Changed the implementation to use the C++0x standard library templates
          <code class="computeroutput"><span class="identifier">array</span></code>, <code class="computeroutput"><span class="identifier">shared_ptr</span></code>,
          <code class="computeroutput"><span class="identifier">weak_ptr</span></code> and <code class="computeroutput"><span class="identifier">atomic</span></code> when they are available, rather
          than the Boost equivalents.
        </li>
<li class="listitem">
          Use C++0x variadic templates when available, rather than generating function
          overloads using Boost.Preprocessor.
        </li>
<li class="listitem">
          Changed exception reporting to include the function name in exception
          <code class="computeroutput"><span class="identifier">what</span><span class="special">()</span></code>
          messages.
        </li>
<li class="listitem">
          Fixed insufficient initialisers warning with MinGW.
        </li>
<li class="listitem">
          Changed the <code class="computeroutput"><span class="identifier">shutdown_service</span><span class="special">()</span></code> member functions to be private.
        </li>
<li class="listitem">
          Added archetypes for testing socket option functions.
        </li>
<li class="listitem">
          Changed the Boost.Asio examples so that they don't use Boost.Thread's convenience
          header. Use the header file that is specifically for the boost::thread
          class instead.
        </li>
<li class="listitem">
          Removed the dependency on OS-provided macros for the well-known IPv4 and
          IPv6 addresses. This should eliminate annoying "missing braces around
          initializer" warnings (<a href="https://svn.boost.org/trac/boost/ticket/3741" target="_top">#3741</a>).
        </li>
<li class="listitem">
          Reduced the size of <code class="computeroutput"><span class="identifier">ip</span><span class="special">::</span><span class="identifier">basic_endpoint</span><span class="special">&lt;&gt;</span></code> objects (such as <code class="computeroutput"><span class="identifier">ip</span><span class="special">::</span><span class="identifier">tcp</span><span class="special">::</span><span class="identifier">endpoint</span></code> and <code class="computeroutput"><span class="identifier">ip</span><span class="special">::</span><span class="identifier">udp</span><span class="special">::</span><span class="identifier">endpoint</span></code>).
        </li>
<li class="listitem">
          Changed the reactor backends to assume that any descriptors or sockets
          added using <code class="computeroutput"><span class="identifier">assign</span><span class="special">()</span></code>
          may have been <code class="computeroutput"><span class="identifier">dup</span><span class="special">()</span></code>-ed,
          and so require explicit deregistration from the reactor (<a href="https://svn.boost.org/trac/boost/ticket/4971" target="_top">#4971</a>).
        </li>
<li class="listitem">
          Removed the deprecated member functions named <code class="computeroutput"><span class="identifier">io_service</span><span class="special">()</span></code>. The <code class="computeroutput"><span class="identifier">get_io_service</span><span class="special">()</span></code> member functions should be used instead.
        </li>
<li class="listitem">
          Removed the deprecated typedefs <code class="computeroutput"><span class="identifier">resolver_query</span></code>
          and <code class="computeroutput"><span class="identifier">resolver_iterator</span></code> from
          the <code class="computeroutput"><span class="identifier">ip</span><span class="special">::</span><span class="identifier">tcp</span></code>, <code class="computeroutput"><span class="identifier">ip</span><span class="special">::</span><span class="identifier">udp</span></code>
          and <code class="computeroutput"><span class="identifier">ip</span><span class="special">::</span><span class="identifier">icmp</span></code> classes.
        </li>
<li class="listitem">
          Modified the <code class="computeroutput"><span class="identifier">buffers_iterator</span><span class="special">&lt;&gt;</span></code> and <code class="computeroutput"><span class="identifier">ip</span><span class="special">::</span><span class="identifier">basic_resolver_iterator</span></code>
          classes so that the value_type typedefs are non-const byte types.
        </li>
<li class="listitem">
          Fixed warnings reported by g++'s <code class="literal">-Wshadow</code> compiler option
          (<a href="https://svn.boost.org/trac/boost/ticket/3905" target="_top">#3905</a>).
        </li>
<li class="listitem">
          Added an explicit cast to convert the <code class="computeroutput"><span class="identifier">FIONBIO</span></code>
          constant to int, to suppress a compiler warning on some platforms (<a href="https://svn.boost.org/trac/boost/ticket/5128" target="_top">#5128</a>).
        </li>
<li class="listitem">
          Changed most examples to treat a failure by an accept operation as non-fatal
          (<a href="https://svn.boost.org/trac/boost/ticket/5124" target="_top">#5124</a>).
        </li>
<li class="listitem">
          Fixed an error in the <code class="literal">tick_count_timer</code> example by making
          the duration type signed. Previously, a wait on an already-passed deadline
          would not return for a very long time (<a href="https://svn.boost.org/trac/boost/ticket/5418" target="_top">#5418</a>).
        </li>
</ul></div>
<h4>
<a name="boost_asio.history.h6"></a>
      <span><a name="boost_asio.history.asio_1_4_9___boost_1_46_1"></a></span><a class="link" href="history.html#boost_asio.history.asio_1_4_9___boost_1_46_1">Asio
      1.4.9 / Boost 1.46.1</a>
    </h4>
<div class="itemizedlist"><ul class="itemizedlist" type="disc">
<li class="listitem">
          <code class="computeroutput"><span class="identifier">EV_ONESHOT</span></code> seems to cause
          problems on some versions of Mac OS X, with the <code class="computeroutput"><span class="identifier">io_service</span></code>
          destructor getting stuck inside the <code class="computeroutput"><span class="identifier">close</span><span class="special">()</span></code> system call. Changed the kqueue backend
          to use <code class="computeroutput"><span class="identifier">EV_CLEAR</span></code> instead
          (<a href="https://svn.boost.org/trac/boost/ticket/5021" target="_top">#5021</a>).
        </li>
<li class="listitem">
          Fixed compile failures with some versions of <code class="literal">g++</code> due
          to the use of anonymous enums (<a href="https://svn.boost.org/trac/boost/ticket/4883" target="_top">#4883</a>).
        </li>
<li class="listitem">
          Fixed a bug on kqueue-based platforms, where some system calls that repeatedly
          fail with <code class="computeroutput"><span class="identifier">EWOULDBLOCK</span></code> are
          not correctly re-registered with kqueue.
        </li>
<li class="listitem">
          Changed <code class="computeroutput"><span class="identifier">asio</span><span class="special">::</span><span class="identifier">streambuf</span></code> to ensure that its internal
          pointers are updated correctly after the data has been modified using
          <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">streambuf</span></code> member functions.
        </li>
<li class="listitem">
          Fixed a bug that prevented the linger socket option from working on platforms
          other than Windows.
        </li>
</ul></div>
<h4>
<a name="boost_asio.history.h7"></a>
      <span><a name="boost_asio.history.asio_1_4_8___boost_1_46"></a></span><a class="link" href="history.html#boost_asio.history.asio_1_4_8___boost_1_46">Asio
      1.4.8 / Boost 1.46</a>
    </h4>
<div class="itemizedlist"><ul class="itemizedlist" type="disc">
<li class="listitem">
          Fixed an integer overflow problem that occurs when <code class="computeroutput"><span class="identifier">ip</span><span class="special">::</span><span class="identifier">address_v4</span><span class="special">::</span><span class="identifier">broadcast</span><span class="special">()</span></code> is used on 64-bit platforms.
        </li>
<li class="listitem">
          Fixed a problem on older Linux kernels (where epoll is used without timerfd
          support) that prevents timely delivery of deadline_timer handlers, after
          the program has been running for some time (<a href="https://svn.boost.org/trac/boost/ticket/5045" target="_top">#5045</a>).
        </li>
</ul></div>
<h4>
<a name="boost_asio.history.h8"></a>
      <span><a name="boost_asio.history.asio_1_4_7___boost_1_45"></a></span><a class="link" href="history.html#boost_asio.history.asio_1_4_7___boost_1_45">Asio
      1.4.7 / Boost 1.45</a>
    </h4>
<div class="itemizedlist"><ul class="itemizedlist" type="disc">
<li class="listitem">
          Fixed a problem on kqueue-based platforms where a <code class="computeroutput"><span class="identifier">deadline_timer</span></code>
          may never fire if the <code class="computeroutput"><span class="identifier">io_service</span></code>
          is running in a background thread (<a href="https://svn.boost.org/trac/boost/ticket/4568" target="_top">#4568</a>).
        </li>
<li class="listitem">
          Fixed a const-correctness issue that prevented valid uses of <code class="computeroutput"><span class="identifier">has_service</span><span class="special">&lt;&gt;</span></code>
          from compiling (<a href="https://svn.boost.org/trac/boost/ticket/4638" target="_top">#4638</a>).
        </li>
<li class="listitem">
          Fixed MinGW cross-compilation (<a href="https://svn.boost.org/trac/boost/ticket/4491" target="_top">#4491</a>).
        </li>
<li class="listitem">
          Removed dependency on deprecated Boost.System functions (<a href="https://svn.boost.org/trac/boost/ticket/4672" target="_top">#4672</a>).
        </li>
<li class="listitem">
          Ensured <code class="computeroutput"><span class="identifier">close</span><span class="special">()</span></code>/<code class="computeroutput"><span class="identifier">closesocket</span><span class="special">()</span></code>
          failures are correctly propagated (<a href="https://svn.boost.org/trac/boost/ticket/4573" target="_top">#4573</a>).
        </li>
<li class="listitem">
          Added a check for errors returned by <code class="computeroutput"><span class="identifier">InitializeCriticalSectionAndSpinCount</span></code>
          (<a href="https://svn.boost.org/trac/boost/ticket/4574" target="_top">#4574</a>).
        </li>
<li class="listitem">
          Added support for hardware flow control on QNX (<a href="https://svn.boost.org/trac/boost/ticket/4625" target="_top">#4625</a>).
        </li>
<li class="listitem">
          Always use <code class="computeroutput"><span class="identifier">pselect</span><span class="special">()</span></code>
          on HP-UX, if it is available (<a href="https://svn.boost.org/trac/boost/ticket/4578" target="_top">#4578</a>).
        </li>
<li class="listitem">
          Ensured handler arguments are passed as lvalues (<a href="https://svn.boost.org/trac/boost/ticket/4744" target="_top">#4744</a>).
        </li>
<li class="listitem">
          Fixed Windows build when thread support is disabled (<a href="https://svn.boost.org/trac/boost/ticket/4680" target="_top">#4680</a>).
        </li>
<li class="listitem">
          Fixed a Windows-specific problem where <code class="computeroutput"><span class="identifier">deadline_timer</span></code>
          objects with expiry times set more than 5 minutes in the future may never
          expire (<a href="https://svn.boost.org/trac/boost/ticket/4745" target="_top">#4745</a>).
        </li>
<li class="listitem">
          Fixed the <code class="computeroutput"><span class="identifier">resolver</span></code> backend
          on BSD platforms so that an empty service name resolves to port number
          <code class="computeroutput"><span class="number">0</span></code>, as per the documentation
          (<a href="https://svn.boost.org/trac/boost/ticket/4690" target="_top">#4690</a>).
        </li>
<li class="listitem">
          Fixed read operations so that they do not accept buffer sequences of type
          <code class="computeroutput"><span class="identifier">const_buffers_1</span></code> (<a href="https://svn.boost.org/trac/boost/ticket/4746" target="_top">#4746</a>).
        </li>
<li class="listitem">
          Redefined <code class="computeroutput"><span class="identifier">Protocol</span></code> and
          <code class="computeroutput"><span class="identifier">id</span></code> to avoid clashing with
          Objective-C++ keywords (<a href="https://svn.boost.org/trac/boost/ticket/4191" target="_top">#4191</a>).
        </li>
<li class="listitem">
          Fixed a <code class="computeroutput"><span class="identifier">vector</span></code> reallocation
          performance issue that can occur when there are many active <code class="computeroutput"><span class="identifier">deadline_timer</span></code> objects (<a href="https://svn.boost.org/trac/boost/ticket/4780" target="_top">#4780</a>).
        </li>
<li class="listitem">
          Fixed the kqueue backend so that it compiles on NetBSD (<a href="https://svn.boost.org/trac/boost/ticket/4662" target="_top">#4662</a>).
        </li>
<li class="listitem">
          Fixed the socket <code class="computeroutput"><span class="identifier">io_control</span><span class="special">()</span></code> implementation on 64-bit Mac OS X and
          BSD platforms (<a href="https://svn.boost.org/trac/boost/ticket/4782" target="_top">#4782</a>).
        </li>
<li class="listitem">
          Fixed a Windows-specific problem where failures from <code class="computeroutput"><span class="identifier">accept</span><span class="special">()</span></code> are incorrectly treated as successes
          (<a href="https://svn.boost.org/trac/boost/ticket/4859" target="_top">#4859</a>).
        </li>
<li class="listitem">
          Deprecated the separate compilation header <code class="computeroutput"><span class="special">&lt;</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">asio</span><span class="special">/</span><span class="identifier">impl</span><span class="special">/</span><span class="identifier">src</span><span class="special">.</span><span class="identifier">cpp</span><span class="special">&gt;</span></code>
          in favour of <code class="computeroutput"><span class="special">&lt;</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">asio</span><span class="special">/</span><span class="identifier">impl</span><span class="special">/</span><span class="identifier">src</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span></code> (<a href="https://svn.boost.org/trac/boost/ticket/4560" target="_top">#4560</a>).
        </li>
</ul></div>
<h4>
<a name="boost_asio.history.h9"></a>
      <span><a name="boost_asio.history.asio_1_4_6___boost_1_44"></a></span><a class="link" href="history.html#boost_asio.history.asio_1_4_6___boost_1_44">Asio
      1.4.6 / Boost 1.44</a>
    </h4>
<div class="itemizedlist"><ul class="itemizedlist" type="disc">
<li class="listitem">
          Reduced compile times. (Note that some programs may need to add additional
          <code class="computeroutput"><span class="preprocessor">#include</span></code>s, e.g. if the
          program uses <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">array</span></code> but does not explicitly include
          <code class="computeroutput"><span class="special">&lt;</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">array</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span></code>.)
        </li>
<li class="listitem">
          Reduced the size of generated code.
        </li>
<li class="listitem">
          Refactored <code class="computeroutput"><span class="identifier">deadline_timer</span></code>
          implementation to improve performance.
        </li>
<li class="listitem">
          Improved multiprocessor scalability on Windows by using a dedicated hidden
          thread to wait for timers.
        </li>
<li class="listitem">
          Improved performance of <code class="computeroutput"><span class="identifier">asio</span><span class="special">::</span><span class="identifier">streambuf</span></code>
          with <code class="computeroutput"><span class="identifier">async_read</span><span class="special">()</span></code>
          and <code class="computeroutput"><span class="identifier">async_read_until</span><span class="special">()</span></code>.
          These read operations now use the existing capacity of the <code class="computeroutput"><span class="identifier">streambuf</span></code> when reading, rather than limiting
          the read to 512 bytes.
        </li>
<li class="listitem">
          Added optional separate compilation. To enable, add <code class="computeroutput"><span class="preprocessor">#include</span>
          <span class="special">&lt;</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">asio</span><span class="special">/</span><span class="identifier">impl</span><span class="special">/</span><span class="identifier">src</span><span class="special">.</span><span class="identifier">cpp</span><span class="special">&gt;</span></code> to one source file in a program, then
          build the program with <code class="computeroutput"><span class="identifier">BOOST_ASIO_SEPARATE_COMPILATION</span></code>
          defined in the project/compiler settings. Alternatively, <code class="computeroutput"><span class="identifier">BOOST_ASIO_DYN_LINK</span></code> may be defined to
          build a separately-compiled Asio as part of a shared library.
        </li>
<li class="listitem">
          Added new macro <code class="computeroutput"><span class="identifier">BOOST_ASIO_DISABLE_FENCED_BLOCK</span></code>
          to permit the disabling of memory fences around completion handlers, even
          if thread support is enabled.
        </li>
<li class="listitem">
          Reworked timeout examples to better illustrate typical use cases.
        </li>
<li class="listitem">
          Ensured that handler arguments are passed as <code class="computeroutput"><span class="keyword">const</span></code>
          types.
        </li>
<li class="listitem">
          Fixed incorrect parameter order in <code class="computeroutput"><span class="identifier">null_buffers</span></code>
          variant of <code class="computeroutput"><span class="identifier">async_send_to</span></code>
          (<a href="https://svn.boost.org/trac/boost/ticket/4170" target="_top">#4170</a>).
        </li>
<li class="listitem">
          Ensured <code class="computeroutput"><span class="keyword">unsigned</span> <span class="keyword">char</span></code>
          is used with <code class="computeroutput"><span class="identifier">isdigit</span></code> in
          <code class="computeroutput"><span class="identifier">getaddrinfo</span></code> emulation (<a href="https://svn.boost.org/trac/boost/ticket/4201" target="_top">#4201</a>).
        </li>
<li class="listitem">
          Fixed handling of very small but non-zero timeouts (<a href="https://svn.boost.org/trac/boost/ticket/4205" target="_top">#4205</a>).
        </li>
<li class="listitem">
          Fixed crash that occurred when an empty buffer sequence was passed to a
          composed read or write operation.
        </li>
<li class="listitem">
          Added missing <code class="computeroutput"><span class="keyword">operator</span><span class="special">+</span></code>
          overload in <code class="computeroutput"><span class="identifier">buffers_iterator</span></code>
          (<a href="https://svn.boost.org/trac/boost/ticket/4382" target="_top">#4382</a>).
        </li>
<li class="listitem">
          Implemented cancellation of <code class="computeroutput"><span class="identifier">null_buffers</span></code>
          operations on Windows.
        </li>
</ul></div>
<h4>
<a name="boost_asio.history.h10"></a>
      <span><a name="boost_asio.history.asio_1_4_5___boost_1_43"></a></span><a class="link" href="history.html#boost_asio.history.asio_1_4_5___boost_1_43">Asio
      1.4.5 / Boost 1.43</a>
    </h4>
<div class="itemizedlist"><ul class="itemizedlist" type="disc">
<li class="listitem">
          Improved performance.
        </li>
<li class="listitem">
          Reduced compile times.
        </li>
<li class="listitem">
          Reduced the size of generated code.
        </li>
<li class="listitem">
          Extended the guarantee that background threads don't call user code to
          all asynchronous operations (<a href="https://svn.boost.org/trac/boost/ticket/3923" target="_top">#3923</a>).
        </li>
<li class="listitem">
          Changed to use edge-triggered epoll on Linux.
        </li>
<li class="listitem">
          Changed to use <code class="computeroutput"><span class="identifier">timerfd</span></code>
          for dispatching timers on Linux, when available.
        </li>
<li class="listitem">
          Changed to use one-shot notifications with kqueue on Mac OS X and BSD platforms.
        </li>
<li class="listitem">
          Added a bitmask type <code class="computeroutput"><span class="identifier">ip</span><span class="special">::</span><span class="identifier">resolver_query_base</span><span class="special">::</span><span class="identifier">flags</span></code>
          as per the TR2 proposal. This type prevents implicit conversion from <code class="computeroutput"><span class="keyword">int</span></code> to <code class="computeroutput"><span class="identifier">flags</span></code>,
          allowing the compiler to catch cases where users incorrectly pass a numeric
          port number as the service name.
        </li>
<li class="listitem">
          Added <code class="computeroutput"><span class="preprocessor">#define</span> <span class="identifier">NOMINMAX</span></code>
          for all Windows compilers. Users can define <code class="computeroutput"><span class="identifier">BOOST_ASIO_NO_NOMINMAX</span></code>
          to suppress this definition (<a href="https://svn.boost.org/trac/boost/ticket/3901" target="_top">#3901</a>).
        </li>
<li class="listitem">
          Fixed a bug where 0-byte asynchronous reads were incorrectly passing an
          <code class="computeroutput"><span class="identifier">error</span><span class="special">::</span><span class="identifier">eof</span></code> result to the completion handler
          (<a href="https://svn.boost.org/trac/boost/ticket/4023" target="_top">#4023</a>).
        </li>
<li class="listitem">
          Changed the <code class="computeroutput"><span class="identifier">io_control</span><span class="special">()</span></code> member functions to always call <code class="computeroutput"><span class="identifier">ioctl</span></code> on the underlying descriptor when
          modifying blocking mode (<a href="https://svn.boost.org/trac/boost/ticket/3307" target="_top">#3307</a>).
        </li>
<li class="listitem">
          Changed the resolver implementation to longer require the typedefs <code class="computeroutput"><span class="identifier">InternetProtocol</span><span class="special">::</span><span class="identifier">resolver_query</span></code> and <code class="computeroutput"><span class="identifier">InternetProtocol</span><span class="special">::</span><span class="identifier">resolver_iterator</span></code>,
          as neither typedef is part of the documented <code class="computeroutput"><span class="identifier">InternetProtocol</span></code>
          requirements. The corresponding typedefs in the <code class="computeroutput"><span class="identifier">ip</span><span class="special">::</span><span class="identifier">tcp</span></code>,
          <code class="computeroutput"><span class="identifier">ip</span><span class="special">::</span><span class="identifier">udp</span></code> and <code class="computeroutput"><span class="identifier">ip</span><span class="special">::</span><span class="identifier">icmp</span></code>
          classes have been deprecated.
        </li>
<li class="listitem">
          Fixed out-of-band handling for reactors not based on <code class="computeroutput"><span class="identifier">select</span><span class="special">()</span></code>.
        </li>
<li class="listitem">
          Added new <code class="computeroutput"><span class="identifier">BOOST_ASIO_DISABLE_THREADS</span></code>
          macro that allows Asio's threading support to be independently disabled.
        </li>
<li class="listitem">
          Minor documentation improvements.
        </li>
</ul></div>
<h4>
<a name="boost_asio.history.h11"></a>
      <span><a name="boost_asio.history.asio_1_4_4___boost_1_42"></a></span><a class="link" href="history.html#boost_asio.history.asio_1_4_4___boost_1_42">Asio
      1.4.4 / Boost 1.42</a>
    </h4>
<div class="itemizedlist"><ul class="itemizedlist" type="disc">
<li class="listitem">
          Added a new HTTP Server 4 example illustrating the use of stackless coroutines
          with Asio.
        </li>
<li class="listitem">
          Changed handler allocation and invocation to use <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">addressof</span></code>
          to get the address of handler objects, rather than applying <code class="computeroutput"><span class="keyword">operator</span><span class="special">&amp;</span></code>
          directly (<a href="https://svn.boost.org/trac/boost/ticket/2977" target="_top">#2977</a>).
        </li>
<li class="listitem">
          Restricted MSVC buffer debugging workaround to 2008, as it causes a crash
          with 2010 beta 2 (<a href="https://svn.boost.org/trac/boost/ticket/3796" target="_top">#3796</a>,
          <a href="https://svn.boost.org/trac/boost/ticket/3822" target="_top">#3822</a>).
        </li>
<li class="listitem">
          Fixed a problem with the lifetime of handler memory, where Windows needs
          the <code class="computeroutput"><span class="identifier">OVERLAPPED</span></code> structure
          to be valid until both the initiating function call has returned and the
          completion packet has been delivered.
        </li>
<li class="listitem">
          Don't block signals while performing system calls, but instead restart
          the calls if they are interrupted.
        </li>
<li class="listitem">
          Documented the guarantee made by strand objects with respect to order of
          handler invocation.
        </li>
<li class="listitem">
          Changed strands to use a pool of implementations, to make copying of strands
          cheaper.
        </li>
<li class="listitem">
          Ensured that kqueue support is enabled for BSD platforms (<a href="https://svn.boost.org/trac/boost/ticket/3626" target="_top">#3626</a>).
        </li>
<li class="listitem">
          Added a <code class="computeroutput"><span class="identifier">boost_</span></code> prefix to
          the <code class="computeroutput"><span class="keyword">extern</span> <span class="string">"C"</span></code>
          thread entry point function (<a href="https://svn.boost.org/trac/boost/ticket/3809" target="_top">#3809</a>).
        </li>
<li class="listitem">
          In <code class="computeroutput"><span class="identifier">getaddrinfo</span></code> emulation,
          only check the socket type (<code class="computeroutput"><span class="identifier">SOCK_STREAM</span></code>
          or <code class="computeroutput"><span class="identifier">SOCK_DGRAM</span></code>) if a service
          name has been specified. This should allow the emulation to work with raw
          sockets.
        </li>
<li class="listitem">
          Added a workaround for some broken Windows firewalls that make a socket
          appear bound to 0.0.0.0 when it is in fact bound to 127.0.0.1.
        </li>
<li class="listitem">
          Applied a fix for reported excessive CPU usage under Solaris (<a href="https://svn.boost.org/trac/boost/ticket/3670" target="_top">#3670</a>).
        </li>
<li class="listitem">
          Added some support for platforms that use older compilers such as g++ 2.95
          (<a href="https://svn.boost.org/trac/boost/ticket/3743" target="_top">#3743</a>).
        </li>
</ul></div>
<h4>
<a name="boost_asio.history.h12"></a>
      <span><a name="boost_asio.history.asio_1_4_3___boost_1_40"></a></span><a class="link" href="history.html#boost_asio.history.asio_1_4_3___boost_1_40">Asio
      1.4.3 / Boost 1.40</a>
    </h4>
<div class="itemizedlist"><ul class="itemizedlist" type="disc">
<li class="listitem">
          Added a new ping example to illustrate the use of ICMP sockets.
        </li>
<li class="listitem">
          Changed the <code class="computeroutput"><span class="identifier">buffered</span><span class="special">*</span><span class="identifier">_stream</span><span class="special">&lt;&gt;</span></code>
          templates to treat 0-byte reads and writes as no-ops, to comply with the
          documented type requirements for <code class="computeroutput"><span class="identifier">SyncReadStream</span></code>,
          <code class="computeroutput"><span class="identifier">AsyncReadStream</span></code>, <code class="computeroutput"><span class="identifier">SyncWriteStream</span></code> and <code class="computeroutput"><span class="identifier">AsyncWriteStream</span></code>.
        </li>
<li class="listitem">
          Changed some instances of the <code class="computeroutput"><span class="keyword">throw</span></code>
          keyword to <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">throw_exception</span><span class="special">()</span></code>
          to allow Asio to be used when exception support is disabled. Note that
          the SSL wrappers still require exception support (<a href="https://svn.boost.org/trac/boost/ticket/2754" target="_top">#2754</a>).
        </li>
<li class="listitem">
          Made Asio compatible with the OpenSSL 1.0 beta (<a href="https://svn.boost.org/trac/boost/ticket/3256" target="_top">#3256</a>).
        </li>
<li class="listitem">
          Eliminated a redundant system call in the Solaris <code class="literal">/dev/poll</code>
          backend.
        </li>
<li class="listitem">
          Fixed a bug in resizing of the bucket array in the internal hash maps (<a href="https://svn.boost.org/trac/boost/ticket/3095" target="_top">#3095</a>).
        </li>
<li class="listitem">
          Ensured correct propagation of the error code when a synchronous accept
          fails (<a href="https://svn.boost.org/trac/boost/ticket/3216" target="_top">#3216</a>).
        </li>
<li class="listitem">
          Ensured correct propagation of the error code when a synchronous read or
          write on a Windows HANDLE fails.
        </li>
<li class="listitem">
          Fixed failures reported when <code class="computeroutput"><span class="identifier">_GLIBCXX_DEBUG</span></code>
          is defined (<a href="https://svn.boost.org/trac/boost/ticket/3098" target="_top">#3098</a>).
        </li>
<li class="listitem">
          Fixed custom memory allocation support for timers (<a href="https://svn.boost.org/trac/boost/ticket/3107" target="_top">#3107</a>).
        </li>
<li class="listitem">
          Tidied up various warnings reported by g++ (<a href="https://svn.boost.org/trac/boost/ticket/1341" target="_top">#1341</a>,
          <a href="https://svn.boost.org/trac/boost/ticket/2618" target="_top">#2618</a>).
        </li>
<li class="listitem">
          Various documentation improvements, including more obvious hyperlinks to
          function overloads, header file information, examples for the handler type
          requirements, and adding enum values to the index (<a href="https://svn.boost.org/trac/boost/ticket/3157" target="_top">#3157</a>,
          <a href="https://svn.boost.org/trac/boost/ticket/2620" target="_top">#2620</a>).
        </li>
</ul></div>
<h4>
<a name="boost_asio.history.h13"></a>
      <span><a name="boost_asio.history.asio_1_4_2___boost_1_39"></a></span><a class="link" href="history.html#boost_asio.history.asio_1_4_2___boost_1_39">Asio
      1.4.2 / Boost 1.39</a>
    </h4>
<div class="itemizedlist"><ul class="itemizedlist" type="disc">
<li class="listitem">
          Implement automatic resizing of the bucket array in the internal hash maps.
          This is to improve performance for very large numbers of asynchronous operations
          and also to reduce memory usage for very small numbers. A new macro <code class="computeroutput"><span class="identifier">BOOST_ASIO_HASH_MAP_BUCKETS</span></code> may be used
          to tweak the sizes used for the bucket arrays. (N.B. this feature introduced
          a bug which was fixed in Asio 1.4.3 / Boost 1.40.)
        </li>
<li class="listitem">
          Add performance optimisation for the Windows IOCP backend for when no timers
          are used.
        </li>
<li class="listitem">
          Prevent locale settings from affecting formatting of TCP and UDP endpoints
          (<a href="https://svn.boost.org/trac/boost/ticket/2682" target="_top">#2682</a>).
        </li>
<li class="listitem">
          Fix a memory leak that occurred when an asynchronous SSL operation's completion
          handler threw an exception (<a href="https://svn.boost.org/trac/boost/ticket/2910" target="_top">#2910</a>).
        </li>
<li class="listitem">
          Fix the implementation of <code class="computeroutput"><span class="identifier">io_control</span><span class="special">()</span></code> so that it adheres to the documented
          type requirements for IoControlCommand (<a href="https://svn.boost.org/trac/boost/ticket/2820" target="_top">#2820</a>).
        </li>
<li class="listitem">
          Fix incompatibility between Asio and ncurses.h (<a href="https://svn.boost.org/trac/boost/ticket/2156" target="_top">#2156</a>).
        </li>
<li class="listitem">
          On Windows, specifically handle the case when an overlapped <code class="computeroutput"><span class="identifier">ReadFile</span></code> call fails with <code class="computeroutput"><span class="identifier">ERROR_MORE_DATA</span></code>. This enables a hack
          where a <code class="computeroutput"><span class="identifier">windows</span><span class="special">::</span><span class="identifier">stream_handle</span></code> can be used with a message-oriented
          named pipe (<a href="https://svn.boost.org/trac/boost/ticket/2936" target="_top">#2936</a>).
        </li>
<li class="listitem">
          Fix system call wrappers to always clear the error on success, as POSIX
          allows successful system calls to modify errno (<a href="https://svn.boost.org/trac/boost/ticket/2953" target="_top">#2953</a>).
        </li>
<li class="listitem">
          Don't include termios.h if <code class="computeroutput"><span class="identifier">BOOST_ASIO_DISABLE_SERIAL_PORT</span></code>
          is defined (<a href="https://svn.boost.org/trac/boost/ticket/2917" target="_top">#2917</a>).
        </li>
<li class="listitem">
          Cleaned up some more MSVC level 4 warnings (<a href="https://svn.boost.org/trac/boost/ticket/2828" target="_top">#2828</a>).
        </li>
<li class="listitem">
          Various documentation fixes (<a href="https://svn.boost.org/trac/boost/ticket/2871" target="_top">#2871</a>).
        </li>
</ul></div>
<h4>
<a name="boost_asio.history.h14"></a>
      <span><a name="boost_asio.history.asio_1_4_1___boost_1_38"></a></span><a class="link" href="history.html#boost_asio.history.asio_1_4_1___boost_1_38">Asio
      1.4.1 / Boost 1.38</a>
    </h4>
<div class="itemizedlist"><ul class="itemizedlist" type="disc">
<li class="listitem">
          Improved compatibility with some Windows firewall software.
        </li>
<li class="listitem">
          Ensured arguments to <code class="computeroutput"><span class="identifier">windows</span><span class="special">::</span><span class="identifier">overlapped_ptr</span><span class="special">::</span><span class="identifier">complete</span><span class="special">()</span></code> are correctly passed to the completion
          handler (<a href="https://svn.boost.org/trac/boost/ticket/2614" target="_top">#2614</a>).
        </li>
<li class="listitem">
          Fixed a link problem and multicast failure on QNX (<a href="https://svn.boost.org/trac/boost/ticket/2504" target="_top">#2504</a>,
          <a href="https://svn.boost.org/trac/boost/ticket/2530" target="_top">#2530</a>).
        </li>
<li class="listitem">
          Fixed a compile error in SSL support on MinGW / g++ 3.4.5.
        </li>
<li class="listitem">
          Drop back to using a pipe for notification if eventfd is not available
          at runtime on Linux (<a href="https://svn.boost.org/trac/boost/ticket/2683" target="_top">#2683</a>).
        </li>
<li class="listitem">
          Various minor bug and documentation fixes (<a href="https://svn.boost.org/trac/boost/ticket/2534" target="_top">#2534</a>,
          <a href="https://svn.boost.org/trac/boost/ticket/2541" target="_top">#2541</a>,
          <a href="https://svn.boost.org/trac/boost/ticket/2607" target="_top">#2607</a>,
          <a href="https://svn.boost.org/trac/boost/ticket/2617" target="_top">#2617</a>,
          <a href="https://svn.boost.org/trac/boost/ticket/2619" target="_top">#2619</a>).
        </li>
</ul></div>
<h4>
<a name="boost_asio.history.h15"></a>
      <span><a name="boost_asio.history.asio_1_4_0___boost_1_37"></a></span><a class="link" href="history.html#boost_asio.history.asio_1_4_0___boost_1_37">Asio
      1.4.0 / Boost 1.37</a>
    </h4>
<div class="itemizedlist"><ul class="itemizedlist" type="disc">
<li class="listitem">
          Enhanced CompletionCondition concept with the signature <code class="computeroutput"><span class="identifier">size_t</span>
          <span class="identifier">CompletionCondition</span><span class="special">(</span><span class="identifier">error_code</span> <span class="identifier">ec</span><span class="special">,</span> <span class="identifier">size_t</span> <span class="identifier">total</span><span class="special">)</span></code>,
          where the return value indicates the maximum number of bytes to be transferred
          on the next read or write operation. (The old CompletionCondition signature
          is still supported for backwards compatibility).
        </li>
<li class="listitem">
          New windows::overlapped_ptr class to allow arbitrary overlapped I/O functions
          (such as TransmitFile) to be used with Asio.
        </li>
<li class="listitem">
          On recent versions of Linux, an eventfd descriptor is now used (rather
          than a pipe) to interrupt a blocked select/epoll reactor.
        </li>
<li class="listitem">
          Added const overloads of lowest_layer().
        </li>
<li class="listitem">
          Synchronous read, write, accept and connect operations are now thread safe
          (meaning that it is now permitted to perform concurrent synchronous operations
          on an individual socket, if supported by the OS).
        </li>
<li class="listitem">
          Reactor-based io_service implementations now use lazy initialisation to
          reduce the memory usage of an io_service object used only as a message
          queue.
        </li>
</ul></div>
<h4>
<a name="boost_asio.history.h16"></a>
      <span><a name="boost_asio.history.asio_1_2_0___boost_1_36"></a></span><a class="link" href="history.html#boost_asio.history.asio_1_2_0___boost_1_36">Asio
      1.2.0 / Boost 1.36</a>
    </h4>
<div class="itemizedlist"><ul class="itemizedlist" type="disc">
<li class="listitem">
          Added support for serial ports.
        </li>
<li class="listitem">
          Added support for UNIX domain sockets.
        </li>
<li class="listitem">
          Added support for raw sockets and ICMP.
        </li>
<li class="listitem">
          Added wrappers for POSIX stream-oriented file descriptors (excluding regular
          files).
        </li>
<li class="listitem">
          Added wrappers for Windows stream-oriented <code class="computeroutput"><span class="identifier">HANDLE</span></code>s
          such as named pipes (requires <code class="computeroutput"><span class="identifier">HANDLE</span></code>s
          that work with I/O completion ports).
        </li>
<li class="listitem">
          Added wrappers for Windows random-access <code class="computeroutput"><span class="identifier">HANDLE</span></code>s
          such as files (requires <code class="computeroutput"><span class="identifier">HANDLE</span></code>s
          that work with I/O completion ports).
        </li>
<li class="listitem">
          Added support for reactor-style operations (i.e. they report readiness
          but perform no I/O) using a new <code class="computeroutput"><span class="identifier">null_buffers</span></code>
          type.
        </li>
<li class="listitem">
          Added an iterator type for bytewise traversal of buffer sequences.
        </li>
<li class="listitem">
          Added new <code class="computeroutput"><span class="identifier">read_until</span><span class="special">()</span></code>
          and <code class="computeroutput"><span class="identifier">async_read_until</span><span class="special">()</span></code>
          overloads that take a user-defined function object for locating message
          boundaries.
        </li>
<li class="listitem">
          Added an experimental two-lock queue (enabled by defining <code class="computeroutput"><span class="identifier">BOOST_ASIO_ENABLE_TWO_LOCK_QUEUE</span></code>) that
          may provide better <code class="computeroutput"><span class="identifier">io_service</span></code>
          scalability across many processors.
        </li>
<li class="listitem">
          Various fixes, performance improvements, and more complete coverage of
          the custom memory allocation support.
        </li>
</ul></div>
<h4>
<a name="boost_asio.history.h17"></a>
      <span><a name="boost_asio.history.asio_1_0_0___boost_1_35"></a></span><a class="link" href="history.html#boost_asio.history.asio_1_0_0___boost_1_35">Asio
      1.0.0 / Boost 1.35</a>
    </h4>
<p>
      First release of Asio as part of Boost.
    </p>
</div>
<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
<td align="left"></td>
<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2012 Christopher M. Kohlhoff<p>
        Distributed under the Boost Software License, Version 1.0. (See accompanying
        file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
      </p>
</div></td>
</tr></table>
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